Short answer
The IW371618 is a reference in IWC's 3716 generation of the Portuguese Chronograph: 41mm steel case, no date, small seconds at 6, a 30 minute totalizer at 12, and the in-house calibre 69355 behind a sapphire caseback. A replica of this watch lives or dies on three things: the case profile, the gap between the two subdials, and the shape of the leaf hands. Get those right and the watch reads correctly across a table. Get them wrong and it looks off from arm's length, no magnification needed.
One warning before anything else. Reference numbers get shuffled constantly in wholesale catalogs, and the -18 suffix is one of the most mislabeled. Ask your source for photos of the actual piece with the dial visible, not a stock image lifted from IWC's site.
What the real watch does, and why it matters
The 3716 generation moved the Portuguese Chronograph from a modified Valjoux base to IWC's own 69355, a column-wheel chronograph with roughly 46 hours of reserve. That change brought a display caseback, a slightly taller case (a touch over 13mm) and a cleaner pusher feel than the older 3714.
Almost no replica at any price carries a true column wheel. That is fine. What you need to know is what they use instead, because that decides how the watch behaves in month six.
The movement question
- 7750-derived clone with running seconds at 6. The most common setup. The base movement puts running seconds at 9, so builders add a transfer gear to move it. That gear adds drag, and it is the reason so many of these watches develop a stuttering seconds hand or stop entirely. Ask directly whether the seconds hand sweeps smoothly with no hesitation at the 12 position.
- Decorated rotor and bridges. Cosmetic only. It looks convincing through the back glass and tells you nothing about reliability.
- Quartz. Exists, cheap, and the seconds hand ticks. Easy to spot and easy to avoid.
The pushers should start, stop and reset with a firm click. Reset should snap the counter back to zero in one motion, not creep there.
Dial and hands
Applied numerals sit proud of the dial and catch light on their edges. Printed indices sit flat and look grey in raking light. Run a finger across a numeral if you can, or ask for a macro shot from the side.
The leaf hands are a frequent tell. Genuine hands are slender with a clean taper and a polished bevel that throws a bright line along the center. Cheap replicas mold them thicker and rounder, and the bevel disappears. Look at the minute hand where it meets the pinion: a sloppy fit shows a visible gap.
Subdial spacing is the other giveaway. On the real 3716 the two counters sit close to the center axis, framed by a printed track that runs tight around them. Replicas built on a wider movement spread the subdials outward and thin the track. Compare a straight-on photo against a reference image at the same angle, not a three-quarter shot.
Case, caseback and engraving
The case should be brushed on the flanks with polished lugs, and the transition between the two should be crisp. Soft, washed-out edges mean heavy buffing and usually a lower grade case set. Caseback engraving on the genuine is deep and sharp, with the reference and serial cleanly struck. Reproduction engraving tends to look shallow with rounded letter edges.
Check the crystal height. A domed sapphire that sits too proud changes the whole silhouette.
Strap and hardware
Most replicas ship with embossed leather pretending to be alligator. Real alligator has irregular scale shapes and a visible edge seam. Embossed leather repeats the same scale pattern. The buckle should be signed and the pin should be thick enough not to bend. This is a cheap part to upgrade and it changes how the watch wears more than most people expect.
Price tiers, plainly
- Entry. Thin case finishing, printed-looking dial details, an unreliable 7750 build. Fine for a photo, not for daily wear.
- Mid. Decent case set, correct subdial spacing, a clone movement with a decorated back. This is where most sensible buyers land.
- Upper. Better dial furniture, closer hand profiles, improved movement finishing and a strap that feels like leather. Diminishing returns past this point.
Questions to send before you pay
- Which movement, and where is running seconds driven from?
- Case diameter and thickness measured with calipers?
- Is the caseback engraved or laser-etched?
- Photos of the dial straight on, plus a macro of the hands?
- What happens on a warranty claim, and who pays return shipping?
One honest note
Replicas are not the real thing and cannot be sold or represented as genuine. Importing and selling counterfeit goods is restricted or illegal in the US and across the EU, and customs seizures happen. Buy with that in mind, keep expectations calibrated to the price, and treat any seller who claims their stock is indistinguishable from IWC as a seller worth skipping.